Blood transfusion is often done for people who have lack of blood or its several components. But sometimes, it’s just an experiment to check whether a young man’s blood when transfused to an old man’s body will mean anything.

That’s what a company called Ambrosia is thinking of doing. It is now recruiting around 600 people aged 35 up to do this blood exchange experiment. The catch is that the people who will participate will have to pay $8,000 to receive blood from a younger person aged below 25. There is no clinical evidence that this will work just yet, but a similar study in mice proved something.

Tony Wyss-Coray from Stanford University once transfused a young mice’s plasma into an older mice. After tests were conducted, it was found that the older mice had better brain connections and stronger muscles in their hearts and other organs. The theory of Wyss-Coray is that some proteins in young blood activated genetic mechanisms that triggered older bodies to have the organs rejuvenated – but this wasn’t proved scientifically just yet.

The lack of foundation of proofs puts the Ambrosia experiment into bad light. But not to tech billionaire Peter Thiel, who is “very, very interested in young people’s blood.”